Raised Access Flooring in workshop

[Alan Lightstone]

My architects had a really intriguing idea for the floor in my workshop. I've decided that I want the dust collection ducting to run under a false floor in the workshop. Don't need the rehash to over/under debate, this is how I've decided to do things.

I was originally going to go with 2x10 or 2x12 floor joists, with plywood over them, screwed to the joists. Vapor barriers over concrete, etc...

They suggested I go with a raised access floor system. Not sure how many people have had experience with them, but they are commercially used in data centers, car show displays, etc...

Having to just put in the supports every 600mm or 24" and allowing the ducting to go diagonally seems to solve many problems.

Anyone with experience with these? Suggestions?

This will be in coastal Florida, so humidity is 4000 percent, although the workshop will be climate controlled, but not all the time.

Also, how to drill holes to allow ducting to pass through seems more difficult with these than just with plywood? Anyone drilled through these before? (I'm thinking a router and a template). These come in a variety of materials. Most have galvanized metal on the underside. Some are pretty finished surfaces on top, some have composite wood, some have calcium sulphate, among others.

[Bryan Lisowski]

If you have the height, it sounds like a good idea, my only hesitation would be the load bearing capacity. When you make the penetration from underneath, you could probably replace that square with plywood.

[Rob Damon]

They can support CRAC units that weight several thousand pounds depending on the style so weight would not be an issue.

They are not cheap. You-tube has a number of videos on the installs.

[Paul Tubergen]

I have used them in control rooms for process plants as a means to get wires into control equipment. The whole room typically has high heat load reducing the relative humidity and lots of air turnover. I would be a bit concerned about condensation forming under the "cold" floor.

[Alan Lightstone]

I've thought about getting the concrete garage floor sealed with epoxy before applying the floor. Would this be effective in eliminating the moisture transmission from the concrete slab to above?

[Greg R Bradley]

It would not work vey well for very long. The moisture barrier will need to go below the concrete slab. Otherwise any moisture will come through the slab. If you seal it with any of the readily available poly or epoxy coatings, the moisture will simply lift the coating off the concrete, at least in enough area to release the pressure. Basically, the impermeable coating needs to be on the outside. Don't underestimate the force of moisture vapor.

[Alan Lightstone]

It would not work very well for very long. The moisture barrier will need to go below the concrete slab. Otherwise any moisture will come through the slab. If you seal it with any of the readily available poly or epoxy coatings, the moisture will simply lift the coating off the concrete, at least in enough area to release the pressure. Basically, the impermeable coating needs to be on the outside. Don't underestimate the force of moisture vapor.

Am I missing something here? My present garage floor is concrete slab that a number of years after installation I had an epoxy coating put on. This is my present workshop. I've never noted any issues of moisture resulting from anything sitting on the floor. And the epoxy coating looks like new. Isn't this what these coatings are made for?

Is this different if a raised access floor is sitting above it? Or is there not an issue.

[Greg R Bradley]

Am I missing something here? My present garage floor is concrete slab that a number of years after installation I had an epoxy coating put on. This is my present workshop. I've never noted any issues of moisture resulting from anything sitting on the floor. And the epoxy coating looks like new. Isn't this what these coatings are made for?

Is this different if a raised access floor is sitting above it? Or is there not an issue.

I understood that you were building a shop. I also understood that you had moisture coming through other slabs and were concerned about the new one.
IF you have moisture coming through a slab from below, even epoxy or polyurethane will not stop the moisture movement as the higher pressure water will find a way even lifting the bond from paint to cement. Air conditioning or dehumidifiers can create a problem since you are lowering the vapor pressure above the paint.

I have one building that used to be a shop. We blasted the floor and used two part poly floor sealer before moving in. It was fine for 20 years until that building was converted to a warehouse and air conditioned. Now you can see damage where the ground is occasionally moist underneath after a heavy rainy winter.

I do think we might have a slightly different problem as it is very possible to drop the inside humidity into single digits at times.

To put it simply: IF you have moisture coming up through a slab, you aren't likely to successfully stop it permanently with a coating. Lowering the humidity in the space above will make it fail sooner.

[Bill McNiel]

I've thought about getting the concrete garage floor sealed with epoxy before applying the floor. Would this be effective in eliminating the moisture transmission from the concrete slab to above?

Alan-A poly vapor barrier and 4" of gravel below the slab should take care of "moisture transmission".

[Alan Lightstone]

Alan-A poly vapor barrier and 4" of gravel below the slab should take care of "moisture transmission".

Bill, the house is already built, so I can't put any barrier or gravel under the slab.

[Bill Dufour]

Look into used. I live near Silicon valley and I hear there are lots of these flooring systems selling used for cheap as computers get smaller and more spread out. Shipping may be a problem.
I assume you mean the kind with a fixed support structure not the shorter self contained modules like below which are too short for duct work.
Bill

I was surprised how much is on ebay. I assume the different makers are not compatable but you could make some wooden supports if needed to splice different makes together.

http://www.ebay.com/itm/Powerflor-Ra...EAAOSw5cNYg8uR

[Bill Dufour]

used tiles look to be cheaper then plywood. I suppose you could lay I joists and place the tiles on top.
Bill

These are in Florida
http://www.ebay.com/itm/COMPUTER-ROO...8AAOSwnQhXpU0o

[Mike Heidrick]

Whats the math to determine the size and length ductwork you could drop into a 24" grid?

[George Yetka]

Whats the math to determine the size and length ductwork you could drop into a 24" grid?

The grid system breaks down to do this. I had to put 10' lengths of copper below one a few weeks ago. They are made up of stands glued or anchored to the floor and hollow tube stock that is about 3/4x3/4 in 2' and 4' increments(maybe longer).

The tiles are a bit heavy made of steel and about 2" thick(not solid) they cut them with circular saws/grinders. A hole saw or jig saw can cut them.

As for weight I roll CRAC units at 2000 lbs quite often

[Bill McNiel]

Bill, the house is already built, so I can't put any barrier or gravel under the slab.

Alan-
4" of gravel and a vapor barrier have been standard under slabs for a long time throughout the country. It is highly probable that this is the existing condition, especially in a wet state like Florida. But I could be very wrong. Have you experienced any signs of moisture transmission?

Just trying to save you some money - Bill